To meet the increasing demand for nucleic acid synthesis, there has been an increase in the variety of designs, and the volume of production of nucleic acid synthesizers. Unfortunately, the currently available synthesizers are not designed to adequately meet the needs of the industry. In particular, available synthesizers are limited in their ability to efficiently synthesize large numbers of oligonucleotides. While synthesizers have been developed to simultaneously synthesize more than one oligonucleotide at a time, such machines are not efficient at the production of different types of nucleic acids simultaneously (e.g., different lengths of nucleic acids) and are unacceptably prone to performance failures and environmental contamination. Furthermore, available synthesizers are not suitably configured for integration into large-scale automated production facilities.
DNA synthesis is presently performed on automated instruments which are capable of concurrently producing multiple DNA segments. Frequently the apparatus uses reaction columns in which a support material for the reaction is positioned within the columns on top of inert, porous filters, referred to as frits. The support material generally has a starter material bound to the support onto which desired oligonucleotides may be synthesized. The reaction columns are placed within the automated apparatus and chemicals are added to the columns in sequence in appropriate amounts in an automated fashion. In order to address today's large demand for high throughput oligosynthesis, most automated apparatuses have a large footprint and take up a great deal of premium laboratory space.
Most currently known automated synthesizers can produce only a few oligonucleotides at a time, which is limited by the number of reaction columns located within the machines. The number of reaction columns is limited as a practical matter by the increased complexity of the plumbing and valving network, as the number of columns increases. In addition, the system must be airtight to avoid contaminating the chemicals with air or water and to avoid human exposure to the chemicals.
U.S. Pat. No. 5,368,823 issued Nov. 29, 1994, and U.S. Pat. No. 5,541,314 issued Jul. 30, 1996, address the need for producing a large number of oligonucleotides by disclosing a method and apparatus for oligonucleotide synthesis in which the plumbing and valving network is simplified. The patents disclose a system in which there is one supply line and one outlet located in the synthesis chamber for the delivery of reagents into the reaction columns. The outlet can be positioned above the inlet end of each of the columns so that nucleotide reagents, capping reagents, deblocking reagents, wash chemicals, etc. can be provided to each of the reaction columns. All of the reagents are located in a supply system which includes reservoirs and valving to connect the reservoirs with the supply line. A flush/prime column is also located within the chamber so that the supply line can be flushed and primed between each different chemical reagent addition. A vacuum source, located outside of the reaction chamber, is connected to the outlet end of the reaction columns to rapidly draw the chemicals from all columns simultaneously, thus leaving the columns dry and ready to receive the next reagent.
The disclosed apparatus in these two patents provides multiple reaction columns, but the single supply line requires flushing and priming between the addition of each reagent. These steps are time consuming and waste reagents. Moreover, a large footprint is required to accommodate a reaction chamber encompassing the moving supply line and the reaction chambers as well as a vacuum source outside of the reaction chamber. The large footprint is a drawback to space-constrained laboratories.
Another group of patents, U.S. Pat. No. 5,472,672 issued Dec. 5, 1995, U.S. Pat. No. 5,529,756 issued Jun. 25, 1996, and U.S. Pat. No. 5,837,858 issued Nov. 17, 1998, addresses the need for high throughput oligosynthesis by disclosing a polymer synthesis apparatus with many stationary supply lines. The patents disclose an apparatus with a head assembly with many nozzles, with each nozzle coupled to a reagent reservoir. Further, a base assembly has at least one reaction well but can utilize 96-well and other plates. A transport mechanism is coupled to the head assembly and/or base assembly to produce relative movement between the two. The transport mechanism moves horizontally to align a selected reaction well and a selected nozzle to deposit a selected liquid reagent into the reaction well for synthesis of a polymer chain. A sliding seal is positioned between the head assembly and the base assembly to form a common chamber that encloses both the reaction wells and nozzles therein. The seal is constantly being rubbed down by the movement of the metal piece back and forth to move the synthesis block. This wearing down of the seal results in a less efficient seal.
Thus, the art is in need of polymer synthesizers that are efficient, flexible, and are amenable to large-scale production and automation for the synthesis of polymer, and more specifically of DNA.